#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
    
    int i;
    char buf1[20] = {0};
    char buf2[20] = {0};
    
again:    
    printf("请输入第一个字符串:");
    scanf("%s",buf1);
    printf("请输入第二个字符串:");
    scanf("%s",buf2);
    int len1 = strlen(buf1);
    int len2 = strlen(buf2);

    if (len1 + len2 > 20)
    {
        printf("你输入的字符串不符合要求,请重新输入!!!\n");
        goto again;
    }
    

    for ( i = 0; i < len2; i++)
    {
        buf1[len1 + i] = buf2[i];
    }
    
    printf("%s",buf1);
    return 0;
}